In the conventional seat belt device for a vehicle which is provided on an automobile or the like, in order to install the seat belts at the shoulders of the occupants of the vehicle correctly suitable at positions for the physique and the sitting height of those occupants, an adjustable shoulder anchor mechanism is provided which engages to fasten, at a vertically adjustable mounting position, an adjustable anchor connected to a joint which supports a webbing. In particular, a widely used type is one with a unit which uses a continuous webbing for both shoulders and laps, in which a slip joint which passes through and supports the middle section of the webbing is connected to the adjustable anchor, making is possible to adjust the vertical mounting position.
An explanation will now be given with reference to FIG. 1 and FIG. 2 which show, respectively, a front elevational view and a cross-sectional view of a conventional example of this type of adjustable shoulder anchor. Shown in these drawings are an adjustment base or guiding member 2 which is installed by means of upper and lower bolts 9 on a chassis 1 of a vehicle. An adjustable anchor or runner 3 is connected to a slip joint 4 which is penetrated by a webbing 11. The adjustable anchor or runner 3 is guided so as to be moved in the vertical direction on the adjustment base 2. Provided on the adjustable anchor 3 is a movable lock pin 5 which can engage a plurality of engaging openings 8 which are provided through the adjustment base 2. The lock pin 5 is energized in the direction orthogonal to the chassis 1 by means of a spring 6 and is thus maintained in engagement with one of the engaging openings 8. The lock pin 5 can be pulled out by means of a knob 7 which is mounted on the side opposite from the chassis 1, so that the engagement is cancelled.
Accordingly, when it is desired to change the height or position of the slip joint 4 which is penetrated by the webbing 11, the knob 7 is drawn toward the inside of the vehicle and the lock pin 5 is withdrawn from the engaging opening 8. The adjustable anchor 3 is therefore caused to move vertically along the adjustment base 2. At a position corresponding to a suitable engaging opening 8, the knob 7 may be released, allowing the lock pin 5 to penetratingly engage the engaging opening 8 by means of the force of the spring 6.
However, in the above conventional example, the adjustment base is mounted by means of the bolts 9 to the chassis 1 of the vehicle, so that when this mounting is performed, the positioning is troublesome and time is required to tighten the bolts 9.
In another conventional example, a bolt tightening section is provided in the middle section of the adjustment base. Because this bolt tightening section is within the path of movement of the adjustable anchor, there is the inconvenience that the adjustable anchor must be secured after moving it to the top or bottom edges. There is also the inconvenience that this produces limitations in the design, inasmuch as the shape of the anchor base and the bolts must be determined so as not to hamper the movement of the adjustable anchor.